Genetic variability may influence individual’s blood pressure response to caffeine intake
Individual differences exist in responses to caffeine. Some people are more sensitive to the effects of caffeine than others. Part of such variability is due to tolerance, but there are indications that it might have a genetic basis as well. A new study published in the American Journal of Clinical Nutrition, evaluated acute blood pressure effects and explored whether they are influenced by gene variants.
The Italian researchers, G. Randa et al., ¹ recruited 110 healthy men who were habitual low coffee consumers (1-3 Italian espressos a day) who had refrained from drinking coffee on the day preceding the study to limit the effects of tolerance. In a double blind placebo controlled trial, the acute blood pressure responses to both decaffeinated coffee (control) and decaffeinated coffee with 3mg added caffeine/kg (the equivalent of approximately 3 espresso shots) were monitored for 2 hours. Blood samples were collected for genetic and plasma caffeine and adrenaline analysis.
The blood pressure responses were highly variable between subjects, with most subjects experiencing an increase in blood pressure, others showing no change, and some even showing blood pressure reductions after caffeine intake. Individual differences in activity of CYP1A2 gene variant, responsible for the caffeine metabolism and often used to discriminate between so called “fast” and “slow” metabolizers, could not explain the BP results. It is possible that the time frame of the study was too short to evaluate the caffeine metabolism.
However, an association was found between gene variants in the adenosine and alpha2 – adrenergic receptors and the systolic blood pressure (SBP) responses to caffeine. This may suggest that an acute increase in SBP after caffeine consumption may be affected by genetic variants of adenosine receptors. Caffeine is an antagonist of adenosine receptors, which normally mediate vasodilatation.
This study provides interesting insights into factors influencing individual responses to caffeine, although the authors advise caution before drawing any firm conclusions. First of all the entire sample size was small for a genetic study and only healthy non-smoking men were included. So the data cannot be extrapolated to the entire population. Moreover, they stated that they did not evaluate clinical endpoints and that the absolute differences in BP were small and mostly in the range of normal values. However, it would be interesting to test the reported associations between gene variants and BP responses in large population-based studies.
For more information on this topic please take a look at http://www.coffeeandhealth.org/topics/coffee-consumption-and-cardiovascular-health-2/
¹G Renda et al, 2011. Genetic determinants of blood pressure responses to caffeine drinking, American Journal of Clinical Nutrition, published online ahead of print.
